Brian Cox: It's the unanswered questions that make particle physics sexy

I would like to give a brief introduction to particle physics and what we hope to achieve with the Large Hadron Collider at The European Organisation for Nuclear Research in Geneva.

Particle physics is the exploration of the world at its smallest. What we have found in the 100 years or so since Rutherford discovered the nucleus is that everything can be made of just four particles, or three in a sense: two quarks, called an up quark and a down quark, and an electron. So the protons and neutrons in your body are made of up and down quarks, with electrons around them – that's atomic structure.

This is an incredible simplification: we have also found another two copies of those particles which is rather strange. So there are in fact 12 fundamental particles of nature as we know at the moment. The copies appear identical. So the electron has got a partner called a "muon" and the electron has also got the "tau". They are heavier but otherwise identical. And we have no idea why those copies exist.

So why is nature built that way? Why does that pattern of 12 particles, eight of which appear to be useless, allow you to build everything in the universe? We have no idea. That's one of the big questions.

Particle physics tries to describe the forces of nature – that's the way that those particles talk to each other. There are four fundamental forces. There is gravity and the other three forces that work in the sub-atomic world: electromagnetism – fridge magnets and electricity; there is weak force which allows the sun to shine and is responsible for radioactive beta- decay; and there is the stronger nuclear force that sticks the nucleus together called "gluons".

Particle physics is the study or the search for the ultimate building blocks of the universe and, in a sense, I feel the wheels are starting to come off our picture of reality. This is why the Large Hadron Collider is being built.

There are huge and fascinating questions it will help to answer. We now know that 95 per cent of the universe is made of the something other than those 12 particles. And we have very little idea what the other 95 per cent is, which is kind of embarrassing.

Brian Cox, a professor of particle physics at Manchester University, was describing why particle physics is sexy at the Battle of Ideas last week